Good anti-jamming ability is required under “Navigation Warfare”. However, radio frequency circuit is one of the key parts affecting the anti-jamming performance of GNSS receivers. According to features of the GNSS receiver on satellite, and considering both weak signal receiving and strong signal receiving, this paper analyzed the method of calculating maximum Jammer-to-Signal Ratio(JSR) J_max which the circuit can realize the gain of each circuit part, aiming at maximize JSR in the whole signal band. Further, the calculation method was simplified for a particular AGC circuit made of resistance network. Lastly, measured results were given for this kind of AGC circuit, which agrees well with the JSR target requirement 35dB. The analytical method can direct the design of not only GNSS receiver, but also various kinds of other receivers.